Renal allograft fibrosis is currently identified using the invasive allograft biopsy procedure in patients with worsening renal function. However, many challenges exist including early diagnosis of fibrosis (see, e.g., Arias et al., Transplantation 91:4 (2011)) and neither serum creatinine nor estimated glomerular filtration rate appears to be an accurate indicator of fibrosis (Yilmaz et al., Transpl Int 20: 608 (2007)). Moreover, the biopsy procedure is costly, complications still occur, sampling errors may bias the diagnosis, and inter-observer variability in grading of biopsies remains a challenge (Huraib et al., Am J Kidney Dis 14:13 (1989); Beckingham et al., Br J Urol 73: 13 (1994); Benfield et al., Transplantation 67: 544 (1999); Sorof et al., Transplantation 60: 1215 (1995); Colvin et al., J Am Soc Nephrol 8: 1930 (1997); Nicholson et al., Kidney Int 58: 390 (2000); Joh et al. Clin Transplant 20 Suppl 15: 53 (2006)).